Federal Highway Administration - Research, Development, and Technology

CONCRETE MATERIALS AND MIX DESIGN FOR ASSURING DURABLE PAVEMENTS

INFLUENCE OF THE ENVIRONMENT

The environment in which a pavement is placed greatly influences the performance of that pavement (4). This influence has two phases or stages: first, when the concrete is placed, and second, over the life of the pavement. Lack of consideration of the environment during either phase can negate otherwise good mix and pavement designs (see Table 2).

Environmental considerations at the time of construction include ambient temperature; fluctuation of ambient temperature; precipitation; relative humidity; solar radiation and wind. All these factors influence the rate of hydration and strength gain, as well as moisture loss and the onset of uncontrolled cracking. The FHWA currently has a study with Transtec, Inc, to investigate the influence of these factors from the time of placement through the first 72 hours of life. Guidelines are being developed to keep stresses within the pavement slab below critical levels at which uncontrolled cracking will occur. In essence the aim is to control the pavement condition so that strength development always exceeds stress development during the early age.

Over the long-term life of the pavement, temperature and moisture variations will produce compressive (increasing temperature and moisture) and tensile (decreasing temperature and moisture) stresses, which will result in overall expansion and contraction, respectively, of the concrete. Contraction of the concrete will lead to increased joint and crack openings, and greater difficulty in maintaining adequate load transfer.

Temperature and moisture gradients through the thickness of the pavement will cause non-uniform expansion or contraction of the concrete, internal stresses, and result in curling and warping in jointed concrete pavement slabs. Additional cracking can result when these deformed slabs are subjected to loading. The influence of all aspects of temperature and moisture variation must be included during the pavement design phase, through consideration of such things as transverse joint spacing, percent reinforcing and the use of load transfer devices. The University of Washington is currently investigating the effects of curling and warping on long-term pavement performance in a study for the FHWA.

Concrete's Role in Pavement & Structural Design Performance | Influence of Construction

http://www.tfhrc.gov/pavement/pccp/concr5.htm